1. Field of the Invention
The present invention relates to an air conditioning system, and particularly, to an air conditioning system in which a central heating and cooling system is combined with an individual heating and cooling system.
2. Description of the Background Art
In general, a unitary air conditioning system is a kind of central heating and cooling system in which cool air or warm air is made by using a heating and cooling device provided in a factory, an office, a hotel, a house or the like, and supplied to each zone through a pipe or a duct provided in a building.
In the unitary air conditioning system, to independently supply the cool or warm air to individual zones by distinguishing a zone requiring cooling or heating and a zone which does not so, a zone controller for distributing the cool or warm air is installed on a duct, or a plurality of heating and cooling devices are individually installed correspondingly to a plurality of zones.
As shown in FIGS. 1 and 2, a conventional unitary air conditioning system includes an outdoor unit 1 fixedly installed outside a building (a two-story building in the drawing); a supply duct 3 installed inside each zone (Z1) and (Z2) in the building, for distributing the cool or warm air to the zones (Z1) and (Z2); a return duct 4 for returning the cool or warm air in each zone (Z1) and (Z2); a central blower unit 2 connected with the outdoor unit 1 by refrigerant pipes, for sending cool or warm air to the supply duct 3; and a zone controller 5 installed between the central blower unit 2 and the supply duct 3 and between the central blower unit 2 and the return duct 4, for controlling a supply and a return of the air to and from the zones (Z1) and (Z2).
The outdoor unit 1 includes a compressor 1a for compressing refrigerant; a first heat exchanger 1b connected to the compressor 1a by refrigerant pipes, for heat exchange between refrigerant and ambient air; an expander 1c for expanding volume of refrigerant and reducing pressure of refrigerant; a four way valve 1d disposed adjacent to the compressor 1a, for circulating a compressed refrigerant discharged from the compressor 1a according to a heating cycle or a cooling cycle; and an accumulator 1e disposed in the vicinity of a refrigerant inlet of the compressor 1a, for filtering a liquefied refrigerant.
The central blower unit 2 includes a second heat exchanger 2a connected to the compressor 1a and the expander 1c by refrigerant pipes, respectively; and a supply fan (not shown) disposed adjacent to the second heat exchanger 2a, for supplying the cool or warm air to the supply duct 3.
A plurality of discharge openings 3a are formed at the supply duct 3 to supply the cool or warm air to a zone requiring cooling or heating, and a plurality of suction openings 4a through which the air of each zone is sucked are formed at the return duct 4.
The zone controller 5 is composed of valves 5a, 5b, 5c and 5d for selectively supplying the cool or warm air to each zone (Z1) and (Z2), wherein the zone controller 5 is installed between the supply duct 3 and the return duct 4 arranged in the corresponding zone (Z1) and (Z2). By the zone controller 5, the cool or warm air is distributed thus to be supplied to each zone (Z1) and (Z2), or be selectively supplied to only one of the zones (Z1) and (Z2).
The conventional air conditioning system having such a structure is operated as follows.
First, in case that a load detected in each zone (Z1) and (Z2) is greater than a preset value, the cool or warm air is simultaneously supplied through the supply duct 3 of each zone (Z1) and (Z2). On the other side, in case that a load of just one of the zones (Z1) and (Z2) is greater than a preset value, the cool or warm air is supplied through the supply duct 3 of the corresponding zone, which requires cooling or heating, by operation of the zone controller 5.
For example, during the cooling operation, a refrigerant compressed by the compressor 1a of the outdoor unit 1 is condensed in the first heat exchanger 1b of the outdoor unit 1, and the condensed refrigerant passes through the expander 1c and then passes through the second heat exchanger 2a of the central blower unit 2, thereby exchanging its heat with the air introduced through the return duct 4. The air cooled in such a manner moves to the supply duct 3 by a supply fan (not shown).
At this time, the zone controller 5 is operated according to a load of each corresponding zone (Z1) and (Z2), thereby cooling the zone that requires cooling.
Meanwhile, during the heating operation, a flow of the refrigerant is converted by operation of the four way valve 1d, and a heating cycle is carried out as a reverse cycle of the cooling cycle.
However, the conventional air conditioning system constructed and operated as described above has following problems.
First, a zone controller for controlling a return and supply of air should be additionally installed when the cool or warm air is to be more intensively supplied to a zone having high loads, such as a kitchen, a sun room, an exercise room or the like in the building. However, operations for an additional installation of the duct and the zone controller are complicated.
Also, to independently correspond to a load of each zone, a plurality of outdoor units and a plurality of central blower units may be installed corresponding to the number of zones. However, it may cause an increase in cost, which is inefficient.